<template>
  <view>
    <view class="scroll-view-container">
      <scroll-view class="left-scroll-view" scroll-y="true" :style="{height: wh + 'px'}">
        <block v-for="(item,index) in cateList" :key="index">
          <view :class="['left-scroll-view-item' , index === active?'active':'']" @click="activeChanged(index)">
            {{item.cat_name}}
          </view>
        </block>
      </scroll-view>
      <scroll-view class="right-scroll-view" scroll-y="true" :style="{height: wh + 'px'}"  :scroll-top="scrollTop">
        <view class="cate-lv2" v-for="(item2 , index2) in cateLevel2" :key="index2">
          <!-- 二级分类的标题 -->
          <view class="cate-lv2-title">/{{item2.cat_name}}/</view>
          <!-- 当前二级分类下的三级分类列表 -->
          <view class="cate-lv3-list">
            <view class="cate-lv3-item" v-for="(item3 , index3) in item2.children" :key="index3"  @click="gotoGoodsList(item3)">
              <!-- 三级分类的图片 -->
              <image :src="item3.cat_icon.replace('dev','web')"></image>
              <!-- 三级分类的文本 -->
              <text>{{item3.cat_name}}</text>
            </view>
          </view>
        </view>
      </scroll-view>
    </view>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        //当前设备的可用高度
        wh: 0,
        cateList: [],
        active: 0,
        cateLevel2: [],
        scrollTop:0
      };
    },
    onLoad() {
      // 用 uni.getSystemInfoSync() 来获取设备的系统信息
      const sysInfo = uni.getSystemInfoSync()
      // console.log(sysInfo);
      this.wh = sysInfo.windowHeight

      this.getCateList()
    },
    methods: {
      async getCateList() {
        // 发起请求
        const {
          data: res
        } = await uni.$http.get('/api/public/v1/categories')
        // console.log(res);
        // 判断是否获取失败
        if (res.meta.status !== 200) return uni.$showMsg()
        // 转存数据
        this.cateList = res.message

        //为二级分类赋值
        this.cateLevel2 = res.message[0].children
      },
      activeChanged(index) {
        this.active = index

        //为二级分类赋值
        this.cateLevel2 = this.cateList[index].children
        
        //让 scrollTop 在0和1之间切换
        this.scrollTop = this.scrollTop === 0?1:0
      },
      gotoGoodsList(item3){
        uni.navigateTo({
          url: '/subpkg/goods_list/goods_list?cid=' + item3.cat_id
        })
      }
    }
  }
</script>

<style lang="scss">
  .scroll-view-container {
    display: flex;

    .left-scroll-view {
      width: 120px;

      .left-scroll-view-item {
        // 行高
        line-height: 60px;
        background-color: #f7f7f7;
        text-align: center;
        font-size: 12px;

        // 激活项的样式
        &.active {
          background-color: #ffffff;
          position: relative;

          // 渲染激活项左侧的红色指示边线
          &::before {
            content: ' ';
            display: block;
            width: 3px;
            height: 30px;
            background-color: #c00000;
            // 绝对定位
            position: absolute;
            left: 0;
            top: 50%;
            transform: translateY(-50%);
          }
        }
      }
    }
  }

  .cate-lv2-title {
    font-size: 12px;
    font-weight: bold;
    text-align: center;
    padding: 15px 0;
  }

  .cate-lv3-list {
    display: flex;
    // 
    flex-wrap: wrap;

    .cate-lv3-item {
      width: 33.33%;
      margin-bottom: 10px;
      display: flex;
      // 纵向布局
      flex-direction: column;
      // 纵向居中
      justify-content: center;
      // 横向居中
       align-items: center;

      image {
        width: 60px;
        height: 60px;
      }

      text {
        font-size: 12px;
      }
    }
  }
</style>
